April 10


Insulin on Board: How Does it Work

By Gabriela

April 10, 2018

Insulin on board is one of the most important features in the smart pumps. When insulin is delivered via the bolus from the pump, it has a specific timeframe in which it can start to reduce the blood sugar levels.

Let’s say 10 unit bolus is administered in the first hour, 30% of it is used up by the body, -3 units, which leaves the body with 7 still working units. In the next hour, another 30% is used up, -2.1, which leaves the body with 4.9 still working units.

During the fourth hour, the remaining 10%, -3 units are used up, which leaves the body with 2.97 still working units.

But, the problem is, that not every person fits this profile. In other words, not everyone has exactly the same rates in a 24h period. That is where the latest smart pumps come in. They have adjustable time frames that can help with these differences.

Here is everything people need to know about insulin on board.

Insulin on Board: How Does It Work

Some people can set their insulin on board at 3.5h or 5h, rather than 4h, as we explained in the example above.

If we want to know what works best for us, we should check our blood glucose level every hour right after getting bolus, to know how our blood sugar will react in that situation.

Before the insulin on board was available, many individuals with diabetes would have high blood sugar (let’s say 250 mg/dl)  for one or two hours after eating. They always needed to get a correction bolus to balance their blood sugar levels.

But, the problem with this is that they often didn’t account for the insulin on board they already had in the body. In the end, the overcorrecting proved more harmful than useful.

Now, with the help of insulin on board, by adjusting a blood sugar of 250 into the pump, this problem is taken care of. The pump accounts for the insulin on board and suggests a separate correction bolus, which can prove useful for avoiding dangerously low blood sugar levels.

Detailed Explanation

Let’s say a person has an insulin sensitivity factor of 50 and a target of 100 mg/dl. To reduce the blood sugar by 50 points, 1 unit of insulin is necessary. For a normal correction bolus, in this situation, 3 units are necessary to get to 100 mg/dl.

With the help of insulin on board-feature, on the pump, the pump will suggest 1 unit based on the patient’s insulin that is working rather than the 3 units.

Also, the insulin on board-feature can also function when the blood glucose is only 95 mg/dl, even after 1 to 2h after eating. It is expected for the blood glucose to rise 60-80 points more than the pre-meal reading.

If blood glucose is taken 90min after consuming food, it will show a reading of 95mg/dl. This could be a red flag. If the pump shows 4 units still working in the system, it might show that the person needs carbohydrates to head off a reduced blood glucose level.

Insulin On Board Tips

Here are the things we should pay attention to.

  • We should be careful when administrating extra insulin, especially before going to sleep. If we are not going to stay awake for 4 hours, we should take less insulin than we would normally do.
  • We should test our blood sugar levels 3 or 4 hours after the last bolus was received.
  • We shouldn’t take a carb and correction boluses more than every 2 hours.
  • It takes 2 hours to know the adequate indication of the effects of our last bolus.
  • We should always know how much insulin is on board when we test 2h after our last meal.
  • To know how much insulin we should take, we should consult with a doctor or physician.
  • We shouldn’t take matters into our own hands. It is always crucial that we consult with a professional if we notice any changes in our body.

Want to Determine Residual Insulin?

This table can help us determine the residual insulin. Be sure to discuss how to use this table with a doctor or physician.

Insulin Left at 1, 2, 3, and 4h After
A Dose of Novolog or Humalog
Dose Given Units Left To Work After:
1 Hr 2 Hr 3 Hr 4 Hr 5 Hr
1 unit 0.80 u 0.60 u 0.40 u 0.20 u 0
2 units 1.60 u 1.20 u 0.80 u 0.40 u 0
3 units 2.40 u 1.80 u 1.20 u 0.60 u 0
4 units 3.20 u 2.40 u 1.60 u 0.80 u 0
5 units 4.00 u 3.00 u 2.00 u 1.00 u 0
6 units 4.80 u 3.60 u 2.40 u 1.20 u 0
7 units 5.60 u 4.20 u 2.80 u 1.40 u 0
8 units 6.40 u 4.80 u 3.20 u 1.60 u 0
9 units 7.20 u 5.40 u 3.60 u 1.80 u 0
10 units 8.00 u 6.00 u 4.00 u 2.00 u 0

I Want to Be Active. What Should I Do?

Aerobic exercises can reduce blood sugar levels. So, it is crucial that we increase our blood sugar more than normal, 150mg/dl for example before we start any active sports competition.

If we experience increased blood sugar levels prior to the competition due to a miscalculated bolus, it is often caused by a frayed of nerves. This stress and anxiety release the cortisol, epinephrine or norepinephrine.

Since many problems can affect the overall blood sugar levels, it is crucial that we use the doctor’s recommended and set parameters on the pump. These pumps will make it easier for us to make decisions and insulin adjustments.

So, consult with a professional to properly deal with this problem.


  • Gabriela

    Co-Founder & Editor-in-Chief of Diabetes Health Page, Fitness trainer and instructor has dedicated her career to educating and informing people for over 10 years. As one of the most passionate diabetes advocates, Gabi has worked tirelessly to ensure that those people receive the education and support they need to properly manage their diabetes and achieve their health, fitness and weight loss goals.

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